Poor sustained treatment engagement limits the effectiveness of all modalities of substance abuse treatment. This study evaluated the efficacy of a novel treatment reengagement intervention for a subset of syringe-exchange program (SEP) participants (N = 113) that had enrolled in treatment as part of a 4-month clinical trial (M. Kidorf et al., 2009). Three reengagement conditions for participants leaving treatment were compared. Motivational referral condition (MRC) participants (n = 31) could attend group sessions that focused on renewing treatment interest. MRC plus incentive (MRC + I) participants (n = 49) could receive modest monetary incentives for attending these sessions and reenrolling in treatment. Standard referral condition participants (n = 33) could not attend groups or receive incentives. Across a 1-year observation window, almost all study participants (86%) were discharged from treatment. MRC + I participants attended more group sessions than MRC participants and were considerably more likely to reenroll in treatment than participants in the other study conditions. Reengagement strategies can further enhance the public health benefits of SEPs by increasing rates of treatment participation over time.